Printing position adjustment mechanism for printer

Abstract

In a printing position adjusting mechanism employed in an image forming apparatus using a continuous form recording medium having perforated tear lines at predetermined intervals, are sensors are provided for detecting a leading edge of the recording medium and outputting a predetermined signal synchronously with the feeding of the recording medium. With the printing position adjusting mechanism, the period of time, between the detection of the leading edge of the continuous sheet and outputting of the predetermined signal, is adjustable. The apparatus starts printing upon receiving the predetermined signal which is outputted after a predetermined time has elapsed after the leading edge of the continuous sheet is detected.

What is claimed is: 
     
       1. An apparatus for forming an image on a recording medium, said apparatus comprising: (a) means for feeding the recording medium;   (b) means for generating a pulse signal, the number of pulses of said pulse signal corresponding to the feeding amount of said recording medium;   (c) means for detecting a predetermined position on said recording medium; and   (d) means for shifting the phase of said pulse signal in relation to said predetermined position of said recording medium, wherein said means for shifting the phase of said pulse signal comprises means for mounting said means for generating a pulse signal, said mounting means being movable to change the position of said means for generating a pulse signal.   
     
     
       2. The apparatus according to claim 1, wherein said means for generating a pulse signal generates pulses synchronously with the feeding of the recording medium. 
     
     
       3. The apparatus according to claim 2, wherein said means for generating a pulse signal comprises a photosensor means and a disk member rotated synchronously with the feeding of the recording medium, said disk member having at least one slit, said photosensor means detecting said at least one slit and generating said pulse signal. 
     
     
       4. The apparatus according to claim 3, wherein said disk member includes a plurality of slits, said plurality of slits being arranged at predetermined angular intervals. 
     
     
       5. The apparatus according to claim 3, wherein said mounting means is movable to change the position where said photosensor means detects said at least one slit. 
     
     
       6. The apparatus according to claim 5, wherein said mounting means is movable in a substantially linear direction. 
     
     
       7. The apparatus according to claim 6, wherein said substantially linear direction is a substantially vertical direction. 
     
     
       8. The apparatus according to claim 6, wherein said substantially linear direction is tangential to said disk member. 
     
     
       9. The apparatus according to claim 1, wherein said recording medium is a continuous form sheet having tear lines at predetermined intervals. 
     
     
       10. The apparatus according to claim 9, wherein a tear line is at said predetermined position of said recording medium. 
     
     
       11. The apparatus according to claim 1, wherein said means for detecting a predetermined position detects a leading end of said recording medium. 
     
     
       12. The apparatus according to claim 1, wherein said means for shifting the phase includes means for setting a predetermined period of time between the detection of the predetermined position and the generation of a first pulse of said pulse signal. 
     
     
       13. The apparatus according to claim 1, wherein said recording medium is a continuous form sheet having longitudinally spaced feed holes along at least one edge thereof, said means for feeding includes tractor means having projections for engaging respective feed holes, said means for generating a pulse signal generating pulses synchronously with movement of said tractor means.